sweat

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sweat

or

perspiration,

fluid secreted by the sweat glands of mammalian skin and containing water, salts, and waste products of body metabolism such as urea. The dissolved solid content of sweat is only one eighth that of an equal volume of urine, the body's main vehicle of salt excretion; however, excessive sweating may produce severe salt loss (see heat exhaustionheat exhaustion,
condition caused by overexposure to sunlight or another heat source and resulting in dehydration and salt depletion, also known as heat prostration. The symptoms are severe headaches, weakness, dizziness, blurred vision, and sometimes unconsciousness.
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). Human sweat glands are of two types, eccrine and apocrine. The eccrine glands, found everywhere on the body surface, are vital to the regulation of body temperature. Evaporation of the sweat secreted by the eccrines cools the body, dissipating the heat generated by metabolic processes. The release of such sweat is usually imperceptible; yet even in cool weather an individual will lose from 1 pt to 3 qt of fluid per day. Only when environmental conditions are especially hot or humid, or during periods of exercise or emotional stress, does the output of sweat exceed the rate of evaporation, so that noticeable beads of moisture appear on the skin. When such conditions are extreme, the body may lose up to 20 qt of fluid per day. Production of sweat is controlled by the temperature-regulating center of the hypothalamus. The apocrine glands, which occur only in the armpits and about the ears, nipples, navel, and anogenital region, are scent glands. They function in response to stress or sexual stimulation, playing no part in temperature regulation. The apocrines exude a sticky fluid quite different from the watery sweat of the eccrines. Apocrine fluid is rich in organic substances that are odorless when fresh but are quickly degraded by bacteria on the skin to produce characteristic odors. Copious sweating in the armpits comes not from the apocrines but from the eccrines interspersed among them.

Sweat

 

a colorless, slightly opalescent fluid secreted by the sweat glands.

Human sweat contains 98 to 99 percent water, about 0.1 percent urea, uric acid, creatinine, serine, fats, volatile fatty acids, cholesterol, and alkaline metal salts, including chlorides (NaCl predominates— about 0.3 percent), phosphates, and sulfates, as well as sulfuric acid esters and aromatic oxygen acids. The secretion of the sebaceous glands is always mixed with the sweat that gathers on the skin surface. The composition of sweat depends on the condition of the body, the intensity of sweat excretion, and the presence of various substances in the blood. Sweat may be acid, with a pH of 3.8–6.2, or alkaline, when there is decomposition of urea and production of ammonia. In man from 0.5 to 10 liters of sweat or more per day are excreted, depending on intensity of muscle work, temperature of the external environment, and the quantity of water imbibed. Thus, with heavy muscle work, sweat contains a significant quantity of lactic acid and nitrogenous substances. In pathological states, sweat may contain glucose (sugar diabetes), bile pigments, cystine (cystinuria), and sometimes erythrocytes (bloody sweat).

sweat

[swet]
(chemistry)
Exudation of nitroglycerin from dynamite due to separation of nitroglycerin from its adsorbent.
(metallurgy)
Exudate of low-melting-point constituents from a metal on solidification.
(physiology)
The secretion of the sweat glands. Also known as perspiration.
(science and technology)
Formation of moisture beads on a surface as a result of concentration.

sweat

1. the secretion from the sweat glands, esp when profuse and visible, as during strenuous activity, from excessive heat, etc.; commonly also called perspiration
2. Chiefly US an exercise gallop given to a horse, esp on the day of a race
References in periodicals archive ?
Teesside Airport has sweated blood to put into place a solid strategy that will act as a launchpad for the whole of the greater Tees Valley regeneration area.
He admits himself that is his best position but even if he ran and tackled for 90 minutes and sweated blood he would never get Mr Blue-Eyed Boy out of the team.
They will prove his hands weren't nailed to the cross - and that he could well have sweated blood.
Since this fluid looks red in the sun, many people used to believe, mistakenly, that hippos sweated blood.
But Paul Dollin's men were made do it the hard way as, to a man, they sweated blood to rescue the tie.
It used to be thought that hippos sweated blood. It has since been found that a hippo's sweat contains a red dye that can act as a sunscreen.
Tell that to the students who've sweated blood and tears over their studies and faced the same doubts and anxieties of every student down the years.